wave from the portion of the electromagnetic spectrum at lower frequencies than microwaves. The wavelengths of radio waves range from thousands of metres to 30 cm. These correspond to frequencies as low as 3 Hz and as high as 1 gigahertz (109 Hz). Radio-wave communications signals travel through the air in a str...

In his book Radio-activity (1904), Rutherford explained that radioactivity results from the spontaneous disintegration of an unstable element into a lighter element, which may decay further until a stable element is finally created. This process of radioactive decay involves the emission of positively charged particles (later to be recognized as helium nuclei) and negatively charged ones......

...is small. As the field created by the ring magnets increases, the injection pulse is timed so that the field and the energy of the particles from the linear accelerator are properly matched. The radio-frequency accelerating devices, usually called cavities, operate on the same principle as a short section of a linear accelerator. The useful beam may be either the accelerated particles that......

A technique known as radio-frequency (RF) current drive employs electromagnetic radiation to generate a steady-state current. Electromagnetic waves are injected into the plasma so that they propagate within the plasma in one direction around the torus. The speed of the waves is chosen to equal roughly the average speed of the electrons in the plasma. The wave electric field (which in a plasma......

process of heating materials through the application of radio waves of high frequency—i.e., above 70,000 hertz (cycles per second). Two methods of radio-frequency heating have been developed. One of these, induction heating, has proved highly effective for heating metals and other materials that are relatively good electric conductors...

The energy states of atoms, ions, molecules, and other particles are determined primarily by the mutual attraction of the electrons and the nucleus and by the mutual repulsion of the electrons. Electrons and nuclei have magnetic properties in addition to these electrostatic properties. The spin-orbit interaction has been discussed above (see Fine and hyperfine structure of......

...cell companies insisted that the government had to allocate to them bigger slices of spectrum or face the possibility of slow growth in the field of wireless Internet access. The most sought-after radio frequencies were those in which signals traveled the farthest and penetrated buildings most effectively, because that would broaden the area served by a single cellular tower and avoid having......

American motion-picture studio that made some notable films in the 1930s and ’40s. Radio-Keith-Orpheum originated in 1928 from the merger of the Radio Corporation of America, the Keith-Albee-Orpheum theatre chain, and the American Pathé production firm. Though it was one of the major studios in Hollywood, RKO spent much of its 25 years’ existence struggling for financial stability....

For atmospheric or space explosions, radio-pulse receivers and light flash and acoustic detectors are used, as well as devices to measure fallout. Aircraft and rockets can be used to collect radioactive debris, while high-altitude satellites carry detectors for gamma rays and other emissions....

...into Spain in 1956. During the Franco regime and the first few years of the constitutional monarchy, there were only two television stations, both part of the government-owned and -controlled Radio-Televisión Española (RTVE). They still broadcast today, solely in Castilian, and have been split into separate organizations: Radio Nacional de España (RNE) and......

...newspapers express diverse political points of view—conservative, liberal, socialist, and communist. Luxembourg’s influence is felt far beyond its borders through the medium of the RTL (Radio-Television-Luxembourg) Group. The group’s early English-language radio service, Radio Luxembourg, played an important role in the history of rock music when it operated as Europe’s premier......

Ion-exchange separations of this kind are widely used; they can be modified by using mixed solvents, like acetone–water, and great selectivity is possible. In the process called “activation analysis,” an unknown sample to be analyzed is bombarded with neutrons, and the radioactive elements thus formed are separated by anion-exchange procedures. Such analysis is especially......

In 1905, shortly after the discovery of radioactivity, the American chemist Bertram Boltwood suggested that lead is one of the disintegration products of uranium, in which case the older a uranium-bearing mineral the greater should be its proportional part of lead. Analyzing specimens whose relative geologic ages were known, Boltwood found that the ratio of lead to uranium did indeed increase......

Radioactive dosage forms, or radiopharmaceuticals, are substances that contain one or more radioactive atoms and are used for diagnosis or treatment of disease. In some cases the radioactive atoms are incorporated into a larger molecule. The larger molecule helps to direct the radioactive atoms to the organ or tissue of interest. In other cases the diagnostic or therapeutic molecule is the......

...spontaneous decay (partial disintegration) of the nuclei of radioactive elements provides decay particles and energy. The energy, composed of emission kinetic energy and radiation, is converted to heat; it has been an important factor in affecting the temperature gradient and thermal evolution of the Earth. Deep-seated elevated temperatures provide the heat that causes rock to deform......

Radioactive implants in the form of metal needles or “seeds” are used to treat some cancers, such as those of the prostate and uterine cervix. They can deliver high doses of radiation directly into the tumour with less effect on distant tissues....

any of several species of the same chemical element with different masses whose nuclei are unstable and dissipate excess energy by spontaneously emitting radiation in the form of alpha, beta, and gamma rays....

Much of the experimental work on phloem transport now is done with the aid of radioactive substances; for example, when radioactive carbon dioxide administered to an illuminated leaf is incorporated into sugar during photosynthesis and carried from the leaf, the velocity of this movement can be measured by determining the arrival of radioactivity at given points along the stem. Whole plants, as......

any of several species of the same chemical element with different masses whose nuclei are unstable and dissipate excess energy by spontaneously emitting radiation in the form of alpha, beta, and gamma rays....

...all emit gamma rays, and a scintillation camera is used to detect gamma-ray emission. The data are assessed with the R wave of the electrocardiogram as a time marker for the cardiac cycle. Radionuclide cineangiography is a further development of radionuclide imaging. These techniques are used to assess myocardial damage, left ventricular function, valve regurgitation, and, with the use......

Radionuclide imaging (radioactive nuclides) provides a safe, quantitative evaluation of cardiac function and a direct measurement of myocardial blood flow and myocardial metabolism. Radionuclide imaging is used to evaluate the temporal progress of cardiac disease, hemodynamics, and the extent of myocardial damage during and after infarction and to detect pulmonary infarction following emboli.......

In isotope scanning, a radioisotope is introduced into the body, usually by means of intravenous injection. The isotope is then taken up in different amounts by different organs. Its distribution can be determined by recording the radiation it emits, and through charting its concentration it is often possible to recognize the presence, size, and shape of various abnormalities in body organs.......

any of four independent sets of unstable heavy atomic nuclei that decay through a sequence of alpha and beta decays until a stable nucleus is achieved. These four chains of consecutive parent and daughter nuclei begin and end among elements with atomic numbers higher than 81, which is the atomic weight of thallium; the members of each set are genetically related by alpha and beta decay. Three of t...

The amount of waste coming out of the nuclear fuel cycle was very small compared with the amount of waste generated by fossil fuel plants. However, spent nuclear fuel was highly radioactive (hence its designation as high-level waste, or HLW), which made it very dangerous to the public and the environment. Extreme care had to be taken to ensure that it was stored safely and securely....

...depend on careful dissection, or cutting apart, of an organism and on accurate descriptions of the parts. The study of the structure of tissues and cells has been extended by the techniques of autoradiography and histochemistry. In the former, a tissue is supplied with a radioactive substance and allowed to utilize it for an appropriate period of time, after which the tissue is prepared......

...to X rays. These unfortunate early experiences eventually led to an awareness of radiation hazards for professional workers and stimulated the development of a new branch of science—namely, radiobiology....

method of age determination that depends upon the decay to nitrogen of radiocarbon (carbon-14). Carbon-14 is continually formed in nature by the interaction of neutrons with nitrogen-14 in the Earth’s atmosphere; the neutrons required for this reaction are produced by cosmic rays interacting with the atmosphere....

...small, short bones (carpal bones) roughly arranged in two rows. The wrist is also made up of several component joints: the distal radioulnar joint, which acts as a pivot for the forearm bones; the radiocarpal joint, between the radius and the first row of carpal bones, involved in wrist flexion and extension; the midcarpal joint, between two of the rows of carpal bones; and various intercarpal....

During use of the radiochemical methods, spontaneous emissions of particles or electromagnetic radiation from unstable atomic nuclei are monitored. The intensity of the emitted particles or electromagnetic radiation is used for quantitative analysis, and the energy of the emissions is used for qualitative analysis. Emissions of alpha particles, electrons, positrons, neutrons, protons, and gamma......

...which meets annually and is responsible for executing decisions of the Plenipotentiary Conference; (4) the General Secretariat, responsible for administrative and financial services; (5) the Radiocommunications Sector, which was formed by the merger of those activities of the former International Consultative Radio Committee and the former International Frequency Registration Board that......

X-rays were discovered by Wilhelm Conrad Röntgen, a German professor of physics, in his laboratory in the University of Würzburg on Nov. 8, 1895. Early on, in radiodiagnosis, use was made of three of the properties of X-rays—their ability to penetrate the tissues, their photographic effect, and their ability to cause certain substances to fluoresce. In penetrating the tissues,......

...of magazines are also published in the country. The number and range of newspapers increased during the 1990s, despite frequent violent attacks directed against journalists by Islamic extremists. Radiodiffusion Télévision Algérienne operates as a broadcasting institution under the Ministry of Information and Culture. Its three radio channels offer programming in Arabic,......

Morocco’s government-owned radio and television network, Radiodiffusion Télévision Marocaine (RTM), broadcasts throughout the country. Radio broadcasts are in Arabic, French, Tamazight, Spanish, and English, while television is broadcast in Arabic, Tamazight, and French. In addition, a private television network is headquartered in Casablanca and a private radio network in......

...and economic crises of the early 1930s and of what he saw as factors contributing to moral and social decay in Argentina led him to write Radiografía de la pampa (1933; X-Ray of the Pampa), a comprehensive psychological study of the Argentine character laden with fatalistic overtones. La cabeza de Goliat: Microscopía de Buenos Aires (1940;......

Lower-energy betatrons in the 7–20-MeV range, however, have been specially constructed to serve as sources of energetic “hard” X-rays for use in medical and industrial radiography. Portable betatrons, operating at energy levels of approximately 7 MeV, have been designed for specialized applications in industrial radiography—for example, to examine concrete, steel, and......

British rock group that was arguably the most accomplished art-rock band of the early 21st century. This revered quintet made some of the most majestic—if most angst-saturated—music of the postmodern era. Formed in the mid-1980s at Abingdon School in Oxfordshire, Radiohead comprised singer-guitarist Thom Yorke (b. October ...

American medical physicist and joint recipient (with Andrew V. Schally and Roger Guillemin) of the 1977 Nobel Prize for Physiology or Medicine, awarded for her development of radioimmunoassay (RIA), an extremely sensitive technique for measuring minute quantities of biologically active substances....

any of several species of the same chemical element with different masses whose nuclei are unstable and dissipate excess energy by spontaneously emitting radiation in the form of alpha, beta, and gamma rays....

any protozoan of the class Polycystinea (superclass Actinopoda), found in the upper layers of all oceans. Radiolarians, which are mostly spherically symmetrical, are known for their complex and beautifully sculptured, though minute, skeletons, referred to as tests. Usually composed of silica, the test is elaborately perforated in a variety of patterns, forming a series either o...

any protozoan of the class Polycystinea (superclass Actinopoda), found in the upper layers of all oceans. Radiolarians, which are mostly spherically symmetrical, are known for their complex and beautifully sculptured, though minute, skeletons, referred to as tests. Usually composed of silica, the test is elaborately perforated in a variety of patterns, forming a series either o...

...than chalk and will not effervesce in acid. Under a high-powered microscope the form of the diatoms can be distinguished. When well hardened, it is called diatomite. Similar siliceous rocks, called radiolarian earth and radiolarite, are formed from the latticelike opaline skeletons of Radiolaria....

...the calcareous oozes include globigerina ooze, containing the shells of planktonic foraminifera, and pteropod ooze, made up chiefly of the shells of pelagic mollusks. The siliceous oozes include radiolarian ooze, comprising essentially brown clay with more than 30 percent of the skeletons of warm-water protozoa, and diatom ooze, containing the frustules (tiny shells) of diatoms. The......

explosive device designed to scatter radioactive material, hence the adjective dirty. Unlike an atomic bomb’s explosive power, which comes from a nuclear chain reaction, the explosive energy of the dirty bomb comes from ordinary conventional explosives such as dynamite or TNT. W...

branch of medicine using radiation for the diagnosis and treatment of disease. Radiology originally involved the use of X-rays in the diagnosis of disease and the use of X-rays, gamma rays, and other forms of ionizing radiation in the treatment of disease. In more recent years radiology has come also to embrace diagnosis by a method of organ scanning with the use of radioactive ...

X-rays were discovered by Wilhelm Conrad Röntgen, a German professor of physics, in his laboratory in the University of Würzburg on Nov. 8, 1895. Early on, in radiodiagnosis, use was made of three of the properties of X-rays—their ability to penetrate the tissues, their photographic effect, and their ability to cause certain substances to fluoresce. In penetrating the tissues,......

Radioactive elements can emit alpha particles (helium nuclei), electrons, and gamma rays (high-energy electromagnetic radiation). The term radioluminescence, therefore, means that an appropriate material is excited to luminescence by a radioactive substance. When alpha particles bombard a crystal phosphor, tiny scintillations are visible to microscopic observation. This is the principle of the......

...may result in a large variety of chemical changes involving the positive ion, the outgoing electron, and the excited states resultant from charge neutralization, as well as (parent) positive-ion fragmentation and ion-molecule reactions. Some such consequences are summarized for a few cases....

instrument for detecting or measuring radiant energy. The term is applied in particular to devices used to measure infrared radiation. Radiometers are of various types that differ in their method of measurement or detection. Those that function by means of an increase in the temperature of the device, such as Herschel’s thermometer, are called thermal detectors. Commonly used t...

In 1905, shortly after the discovery of radioactivity, the American chemist Bertram Boltwood suggested that lead is one of the disintegration products of uranium, in which case the older a uranium-bearing mineral the greater should be its proportional part of lead. Analyzing specimens whose relative geologic ages were known, Boltwood found that the ratio of lead to uranium did indeed increase......

...In addition, electro-optic detectors collect data on the responses of minerals when exposed to infrared, visible, and ultraviolet light. The same principle, only using gamma radiation, is called radiometric separation....

...widely heard throughout the country—more than 90 percent of the time on some stations—thus furthering appreciation of national culture. At the same time, the radionovela (“soap opera”), a format that would greatly expand with television, got its start. Only in the 1940s were regulations loosened sufficiently to allow use of......

any of several species of the same chemical element with different masses whose nuclei are unstable and dissipate excess energy by spontaneously emitting radiation in the form of alpha, beta, and gamma rays....

...all emit gamma rays, and a scintillation camera is used to detect gamma-ray emission. The data are assessed with the R wave of the electrocardiogram as a time marker for the cardiac cycle. Radionuclide cineangiography is a further development of radionuclide imaging. These techniques are used to assess myocardial damage, left ventricular function, valve regurgitation, and, with the use......

Radionuclide imaging (radioactive nuclides) provides a safe, quantitative evaluation of cardiac function and a direct measurement of myocardial blood flow and myocardial metabolism. Radionuclide imaging is used to evaluate the temporal progress of cardiac disease, hemodynamics, and the extent of myocardial damage during and after infarction and to detect pulmonary infarction following emboli.......

Radioactive dosage forms, or radiopharmaceuticals, are substances that contain one or more radioactive atoms and are used for diagnosis or treatment of disease. In some cases the radioactive atoms are incorporated into a larger molecule. The larger molecule helps to direct the radioactive atoms to the organ or tissue of interest. In other cases the diagnostic or therapeutic molecule is the......

In general, dividing cells (such as cancer cells) are more radiosensitive than nondividing cells. As noted above, a dose of 1–2 Sv is sufficient to kill the average dividing cell, whereas nondividing cells can usually withstand many times as much radiation without overt signs of injury. It is when cells attempt to divide for the first time after irradiation that they are most apt to die......

...illuminated not only directly by a light source such as the Sun or a lamp but also more diffusely by reflected light from other objects. This type of lighting is re-created in computer graphics by radiosity techniques, which model light as energy rather than rays and which look at the effects of all the elements in a scene on the appearance of each object. For example, a brightly coloured......

balloon-borne instrument for making atmospheric measurements, such as temperature, pressure, and humidity, and radioing the information back to a ground station. Special helium-filled meteorological balloons made of high-quality neoprene rubber are employed for elevating the radiosonde to very high altitudes of around 30,000 m (100,000 feet); maximum altitude for balloon-borne radiosondes is abou...

radio communication by means of Morse Code or other coded signals. The radio carrier is modulated by changing its amplitude, frequency, or phase in accordance with the Morse dot-dash system or some other code. At the receiver the coded modulation is recovered by an appropriate demodulator and the code groups are converted into the corresponding symbols. In ma...

In many cases this partnership is nominal and historical rather than substantial and actual. The outstanding example is Radiotelevisione Italiana (RAI), originally founded in 1924. In 1927 an agreement was made with the government for a 25-year broadcasting concession. The charter was extended to cover television in 1952. Two years later a government agency acquired control, and in 1985 it......

...William Ramsay, who was interested in radioactivity. While working on a crude radium preparation that Ramsay had given to him to purify, Hahn showed that a new radioactive substance, which he called radiothorium, was present. Fired by this early success and encouraged by Ramsay, who thought highly of him, he decided to continue with research on radioactivity rather than go into industry. With.....

There are techniques that measure metabolism in the myocardium using the radiotracer method (i.e., a radioactive isotope replaces a stable element in a compound, which is then followed as it is distributed through the body). Positron emission tomography uses positron radionuclides that can be incorporated into true metabolic substrates and consequently can be used to chart the course of......

...ulna bones of the forearm. The wrist is composed of eight or nine small, short bones (carpal bones) roughly arranged in two rows. The wrist is also made up of several component joints: the distal radioulnar joint, which acts as a pivot for the forearm bones; the radiocarpal joint, between the radius and the first row of carpal bones, involved in wrist flexion and extension; the midcarpal......

annual or biennial plant in the mustard family (Brassicaceae), grown for its large succulent taproot. The common radish is likely of Asian or Mediterranean origin and is cultivated worldwide. Radish roots are low in calories and are usually eaten raw; the young leaves can be cooked like spinach. The young fruits are also edible and are often...

chemical element, a heavy radioactive gas of Group 18 (noble gases) of the periodic table, generated by the radioactive decay of radium. (Radon was originally called radium emanation.) Radon is a colourless gas, 7.5 times heavier than air and more than 100 times heavier than hydrogen. ...

...1906 Henri Becquerel, the French physicist who discovered radioactivity, accidentally burned himself by carrying radioactive materials in his pocket. Noting that, Pierre Curie, the co-discoverer of radium, deliberately produced a similar burn on himself. Beginning about 1925, a number of women employed in applying luminescent paint that contained radium to clock and instrument dials became ill....

Other radioisotopes do not belong to the uranium series. For example, radium-224, which is deposited mainly on bone surfaces, has been used in Europe to treat ankylosing spondylitis. Because of its short half-life (3.6 days), it affects only the bone surface and not the bone marrow. Its major toxicity is the production of bone cancer. Like uranium-238, plutonium-239, which is used in some......

Thirty-four isotopes of radium, all radioactive, are known; their half-lives, except for radium-226 (1,600 years) and radium-228 (5.75 years), are less than a few weeks. The long-lived radium-226 is found in nature as a result of its continuous formation from uranium-238 decay. Radium thus occurs in all uranium ores, but it is more widely distributed because it forms water-soluble compounds;......

Thirty-four isotopes of radium, all radioactive, are known; their half-lives, except for radium-226 (1,600 years) and radium-228 (5.75 years), are less than a few weeks. The long-lived radium-226 is found in nature as a result of its continuous formation from uranium-238 decay. Radium thus occurs in all uranium ores, but it is more widely distributed because it forms water-soluble compounds;......

in anatomy, the outer of the two bones of the forearm when viewed with the palm facing forward. All land vertebrates have this bone. In humans it is shorter than the other bone of the forearm, the ulna....

Consider a coordinate system, as shown in Figure 8A, with the circle centred at the origin. At any instant of time, the position of the particle may be specified by giving the radius r of the circle and the angle θ between the position vector and the x-axis. Although r is constant, θ increases uniformly with time t, such that θ = ωt, or......

half the distance between the nuclei of identical neighbouring atoms in the solid form of an element. An atom has no rigid spherical boundary, but it may be thought of as a tiny, dense positive nucleus surrounded by a diffuse negative cloud of electrons. The value of atomic radii depends on the type of chemical bond in whi...

Flush-pin gauges have one moving part and are used to gauge the depth of shoulders or holes. Form gauges are used to check the profile of objects; two of the most common types are radius gauges, which are packs of blades with both concave and convex circular profiles that are used to check the radii of grooves and corners, and screw-thread pitch gauges, which are blades with triangular......

.... . . converges to a specific function, that function will be the required solution of the problem. The largest value of ε for which the sequence converges is called the radius of convergence of the solution....

where k is a distance called the radius of gyration. Comparison to equation (79) shows that k is a measure of how far from the centre of mass the mass of the body is concentrated. Using equations (87) and (88) in equation (86), one finds that...

...wife’s clan until full bridewealth is paid. Identified by a common ancestor and a geographic location, clans traditionally acted also as political units until the Dutch instituted the office of radja. Originally the Ngada recognized a high god (Déva) and his female component (Nitu), but since 1920 missionaries have worked among the Ngada, and today many Ngada are Roman......

German athlete who set several middle-distance running records between 1927 and 1930. Her victory in the 800-metre race at the 1928 Olympic Games—the first Olympics to include women’s athletics—set a world record that was not broken for 16 years....

German athlete who set several middle-distance running records between 1927 and 1930. Her victory in the 800-metre race at the 1928 Olympic Games—the first Olympics to include women’s athletics—set a world record that was not broken for 16 years....

June 30, 1915Elizabeth, N.J.Feb. 17, 2002Tel Aviv, IsraelAmerican-born Israeli nuclear physicist who helped build the world’s first nuclear-powered submarine, the USS Nautilus, in the early 1950s and, later in his career, worked on developing a nuclear reactor fuel that woul...

German scholar and government adviser who made fundamental contributions to the knowledge of the ethnography, folklore, culture, ancient texts, and linguistics of the Turkic peoples of Southern Siberia and Central Asia....

German scholar and government adviser who made fundamental contributions to the knowledge of the ethnography, folklore, culture, ancient texts, and linguistics of the Turkic peoples of Southern Siberia and Central Asia....

German scholar and government adviser who made fundamental contributions to the knowledge of the ethnography, folklore, culture, ancient texts, and linguistics of the Turkic peoples of Southern Siberia and Central Asia....

Krebs received a medical degree from Washington University (St. Louis, Mo.) in 1943 and did research there from 1946 to 1948 under the biochemists Carl and Gerty Cori. In 1948 he joined the faculty of biochemistry at the University of Washington, Seattle, and became a full professor in 1957. He moved in 1968 to the University of California at Davis and returned to the University of Washington......

historic county, east-central Wales, on the English border. It covers an area of mountainous terrain and highlands, including Radnor Forest, with a central valley formed by the River Wye. Radnorshire lies completely within the present county of Powys....

...and Socialist ideas were expressed in great poetic tableaux and in poems probing the subconscious, and by Gyula Illyés, who found inspiration in the life of the peasantry. The poetry of Miklós Radnóti reached a tragic climax in the serene and polished poems he wrote in the last years of his life....

...solutions for specific boundaries had been obtained through the years, it was not until 1931 that the American mathematician Jesse Douglas (and independently the Hungarian American mathematician Tibor Radó) first proved the existence of a minimal solution for any given “simple” boundary. Furthermore, Douglas showed that the general problem of mathematically finding the......

city, Mazowieckie województwo (province), east-central Poland. It is a rail junction and an administrative and industrial centre; the economy of the city relies predominantly on textile milling, glassworks and chemical works, munitions and footwear manufacturing, and food processing. Radom has a museum, a theatre, and a sc...